Within the field of material science, there has been an increasing study and development of shape memory polymers and shape memory alloys. A shape memory polymer (“SMP”) is a type of smart material with the ability to return from a deformed state (temporary shape) to its original (e.g., baseline, memorized, permanent) shape induced by an external stimulus. For example, an SMP can exhibit change from a rigid state to an elastic state, then back to the rigid state using an external stimulus. The SMP in the elastic state can recover its “permanent” shape if left unrestrained. In similar respects, a shape memory alloy (“SMA”) is an alloy that remembers its original shape and after undergoing deformation, is able to transform back to its pre-deformed, original shape when triggered to do so.
Further, an effort in researching and implementing manufacturing processes for 4D printing technology—i.e., self-organizing and/or self-assembly materials—has begun. 4D printing is directed towards the evolution of a fourth dimension in traditional 3D printing, where an object produced and fixed in one shape can later be changed to take on a new shape. For example, a material comprising SMPs or SMAs is created with an initial configuration using a 3D printer and thereafter, the “programmed” or “memorized” reshaping of the SMPs or SMAs applies a time factor/dependence to the configuration.
Some attempts have been made to develop applications for 4D printing technology and/or shape memory materials. For example, Chinese Patent No. 103160948 to Luo discloses a rapid prototyping of shape memory polymer materials using 4D printing. The method of prototyping involves: using a 3D printer to print the SMP material suitable for a 3D object; heating the SMP material to a transition temperature; imposing an external force on the softened SMP material to stretch or twist it; cooling down the SMP material while maintaining the deformation in order to fix a temporary shape; and wherein the SMP material can spontaneously recover from the deformation and return to its original shape in the presence of an appropriate condition. However, the printed SMP material and method of making such material does not include self-assembly capabilities. That is, Luo fails to teach the material having properties concerning self-application and positioning around an underlying object. Further, the printed material is not configured to be shape-adaptive such that the material self-assembles around an underlying object and adapts in shape when there is a change in the shape and profile of the underlying object.
U.S. Patent Application No. 2013/0303957 to Bauerfeind is directed to a medical bandage which can be manually applied to a body part, wherein the bandage has one or more SMP materials that convert between an expanded form and a contracted form to provide support and compression. The bandage may comprise two SMP materials configured as counteracting actuators, in the manner of flexor and extensor, in order to provide quasi-reversible shape transition as a whole from a first shape to a second shape and back. However, this reference does not teach the bandage as being 4D-printed and having the capability to self-assemble around the underlying object and provide adaptive adjustment in shape when there is a change in the shape and profile of the underlying object. Instead, the bandage can be converted from the expanded form, which merely facilitates manual application of the bandage to the body, to the contracted form for compression effect. A person is still required to generally position and orient the bandage with respect to the body part being wrapped. Furthermore, the bandage of Luo is not designed to provide and maintain a specified amount of pressure on the underlying object, even if the underlying object changes in shape, size and/or profile.
U.S. Pat. No. 8,734,703 to Havens et al. discloses an SMP apparatus used to mold and cure a composite material into a composite part having a particular shape. A method of using the apparatus includes applying a composite material to the apparatus, triggering a change in modulus of the apparatus from a rigid state to a malleable state, heating the composite material to a cure temperature, and inducing a pressure differential that drives the apparatus toward the composite material during cure to compress the composite material against a rigid mold. However, the apparatus of Havens does not involve 4D-printing and does not have the capability to self-assemble around an underlying object and readily adjust its shape when the underlying object changes in size and/or shape.
Other references have shown that shape memory materials can be useful in various applications ranging from, for example, shrink wrapping and shrink tubing to medical immobilization and/or fixation devices (e.g., casts, splints, braces). However, a drawback present in these applications is the requirement that the shape memory material be manually or mechanically positioned and/or applied around the underlying object (e.g., shipping crate, injured body part). Further, prior art shape memory materials rely on the chemical characteristics of the particular SMP/SMA used to give one or two different end shape results/permutations, with no gradual or intermediate shapes based on feedback. For instance, after initial setting of the prior art shape memory material, the object underlying the shape memory material may expand and/or contract. The prior art shape memory material—which fail to provide gradualism and intermediate shapes—may cease to be fitted accurately on the underlying object and/or correspond in shape to the underlying object.
Therefore, it would be beneficial to provide a smart material or apparatus which can self assemble around an object without requiring manual or mechanical placement or maneuvering of the device relative to the object. It is further beneficial to provide a device or apparatus which can maintain accurate alignment and fit with the underlying object despite the object expanding or contracting and/or changing shape.